Keith Dysart wrote:
These 90 degrees that Cecil insists are "always"
present are quite difficult to locate.

For anyone who knows how to use a Smith Chart,
those degrees are quite easy to locate.
--
73, Cecil http://www.w5dxp.com

Tom Donaly wrote:
Cecil Moore wrote:
Tom Donaly wrote:
Yes, but not using it very well, or you would have been
able to answer the math problem I posed to you.

I'm sorry, Tom, I didn't even read the math problem
you posed to me as I don't have time for it right
now. I'm sure anyone could use the distributed
network model to solve your problem, even you.

Never mind.

If you really think you have invented an example for
which the distributed network model will give erroneous
results, you really should present it.
--
73, Cecil http://www.w5dxp.com

Gene Fuller wrote:
Cecil Moore wrote:
Gene Fuller wrote:
I believe you said you saw about a 7% shift between the two inputs to
your scope.

I don't recall saying anything like that. I don't even
know what that means. 7% of what?

Sorry, English is not my native language this month. I must have
misinterpreted the following message sent by you (11/30/2007, 3:35 pm).

I've described it before. I used a dual-trace
100 MHz O-scope and estimated the phase angle
between the two traces at about 7% of a cycle.

Sorry, I obviously made an error. It should have
been about 10% of a cycle.
--
73, Cecil http://www.w5dxp.com

Roy Lewallen wrote:

Please fire up EZNEC and tell us how much current phase
shift is reported for 45 degrees of a 1/2WL dipole.

Can anyone point me to any reference to "standing-wave current" in any
reputable text?

"Transmission Lines", by Chipman, Chapter 8

A periodic waveform with no phase information? Huh?

Yes!!! Here's what Chipman says on page 159: "V(d)=A*cos(Bd).
This expression indicates that in the voltage standing wave
pattern produced on a lossless transmission line by a voltage
reflection coefficient, rho, at the terminal load end, the
*phase is constant over any half wavelength* of the pattern
between successive points of zero voltage magnitude, ..."

The same is true for the current standing wave pattern on
a standing-wave antenna and means that constant phase current
cannot be used for delay measurements.

"PHASE IS CONSTANT OVER ANY HALF WAVELENGTH" including the
part where the coil is located.

Please look at the phase of the current in a 1/2WL dipole
and tell us how to use phase measurements of that current
to determine the delay through the 1/2WL dipole wire.

There's no mystery about traveling or standing waves ...

Roy, please explain the phase shift reported by EZNEC for:

http://www.w5dxp.com/coil512.ez

Use the "Load Dat" button to view the phase shift.
--
73, Cecil http://www.w5dxp.com

AI4QJ wrote:
Roy, this is the part I don't understand about some people posting on this
thread. A standing wave does *not* have a phase shift.

Robert A. Chipman agrees with you. He says the standing
wave phase is "... constant over any half wavelength ..."

Kraus also agrees. Here is a graphic from Kraus' book,
"Antennas", showing the lack of phase shift over the length
of a 1/2WL dipole. Essentially the same thing would be true
for short loaded dipoles and loaded mobile antennas.

http://www.w5dxp.com/krausdip.jpg

Roy admitted some time ago that EZNEC reports that
same constant phase for current over the entire length
of a 1/2WL dipole yet he still insists that same current
can be used to measure phase-shift/delay through a coil
when it cannot even be used to measure the phase shift
through 1/2WL of wire.
--
73, Cecil http://www.w5dxp.com

Roy Lewallen wrote:
Can anyone point me to any reference to "standing-wave current" in any
reputable text?

Will Kraus do? Here's a graphic from his book, "Antennas".
Please look at the phase of the current over the entire
1/2WL dipole. EZNEC and Chipman agree with Kraus.

http://www.w5dxp.com/krausdip.jpg
--
73, Cecil http://www.w5dxp.com

AI4QJ wrote:

Roy, this is the part I don't understand about some people posting on this
thread. A standing wave does *not* have a phase shift. The standing wave
stays in a single position and oscillates. The forward and reflected waves
are traveling. An excellent conceptualization of we mean by "standing wave"
with its constructive and destructive interference can be seen he

http://www.chemmybear.com/standing.html

My only problem is, you are the antenna software design guru. I know I must
be missing something big here because I would expect you to be telling
"others" this stuff.

You've described a standing wave, but haven't defined any special kind
of current known as "standing wave current". A standing wave isn't a
current, it's the shape of the magnitude of the voltage or current as a
function of position. I'm sure you can find multiple descriptions of
this on the web, with some being correct and well done, some being
totally wrong, and others at all points between. I tend to look to
published texts for accurate information, and currently have about 14
reputable texts involving transmission lines and electromagnetic waves
on my bookshelf. I surely might have missed it, but I don't recall ever
seeing a reference to "standing wave current" in any of them.

The nature of a standing wave is well known. It describes the envelope
of the distribution of voltage or current on a transmission line
resulting from the sum of forward and reverse traveling waves along a
line not terminated in its characteristic impedance. This envelope,
which has a physical periodicity along the line and which is sinusoidal
in shape only if the SWR is infinite, appears to stand still except for
increasing and decreasing in amplitude at the same rate as the traveling
waves which cause it. So "standing wave current" translates to "envelope
of an interference pattern current". There is no special kind of current
known as "standing wave current" because the combination of words is
meaningless.

Traveling waves interfere to cause the standing wave envelope, as I hope
your web references tell you. When you measure the current at some point
in a transmission line, you're measuring the current at that point,
period. Not "traveling wave current" or some other special kind of
current. The current at any point along a transmission line has a
magnitude and a phase relative to an arbitrary reference. Both can be
easily calculated from basic transmission line principles. You can do it
directly or by adding forward and reflected waves to get the total -- if
you get different results by using the two methods, you've done
something wrong.

For the record, I measured some currents in a wire on both sides of an
inductor at the base of an antenna a couple of years ago and posted the
results here. One of the things I measured, with some care, was the
phase angle between those currents. I didn't "mistakenly" measure
"standing wave current". There is no such thing. I measured sinusoidal
currents, which have phase and magnitude, at two points. The
measurements agreed quite closely with results predicted from
conventional theory. I never was able to tell whether they agreed with
Cecil's theory because he kept changing his predictions.

Note the assertion on the graphic that two waves can be at the same place at
the same time (a subject of a different thread), something I agree with :-)

You'll have to run that one by Cecil. He's said many times that
traveling waves bounce off each other when they meet. That behavior
seems to be necessary to support one of this theories.

Roy Lewallen, W7EL

AI4QJ wrote:
Roy, this is the part I don't understand about some people posting on this
thread. A standing wave does *not* have a phase shift.

Gene said the same thing many months ago:

Gene Fuller, W4SZ wrote:
In a standing wave antenna problem, such as the one you describe,
there is no remaining phase information. Any specific phase
characteristics of the traveling waves died out when the startup
transients died out.

Phase is gone. Kaput. Vanished. Cannot be recovered. Never to be
seen again.
--
73, Cecil http://www.w5dxp.com

AI4QJ wrote:
"Roy Lewallen" wrote in message
...
Or why "virtually no phase information" exists in it. A periodic waveform
with no phase information? Huh?


Or do you mean that the amplitude of the standing wave does contain phase
information about phase 2 other waves, the forward and reflected waves,
relative to each other? Is that what you are saying (making this a semantic
issue again)? The standing wave itself is at zero phase angle.

Hopefully my other posting has mostly answered this.

The total current is the sum of forward and reflected waves. The
magnitude of this total has a periodic distribution, or envelope, alsong
the length of the line known as a standing wave. You can learn certain
things about the line and load by looking at the magnitude and position
of this envelope. The position of the envelope can very reasonably be
termed its "phase", although like the envelope making up the "wave",
it's a positional phase rather than a time related one. But neither the
amplitude nor the "phase" of the envelope known as the standing wave
will, by itself, tell you anything about the phase of the current at any
point along the line.

Confusion among the wave-like envelope of the standing wave, moving
traveling waves, positional and time related phase, and other
potentially ambiguous terms has been instrumental in sustaining
confusion about issues that aren't really very complicated.

Roy Lewallen, W7EL

Roy Lewallen wrote:
You've described a standing wave, but haven't defined any special kind
of current known as "standing wave current".

"Standing wave current" is the current that exists in standing-
wave antennas and stubs. It's phase is constant and cannot
be used to measure phase-shift/delay. EZNEC agrees.

Here is Kraus' graph of standing wave current.

http://www.w5dxp.com/krausdip.jpg

This is a graph of the currents you used for your measurements.
Note the virtually unchanging phase.

For the record, I measured some currents in a wire on both sides of an
inductor at the base of an antenna a couple of years ago and posted the
results here. One of the things I measured, with some care, was the
phase angle between those currents. I didn't "mistakenly" measure
"standing wave current".

EZNEC says that the phase angles of the currents you measured
are unchanging. An unchanging phase is useless for measuring
phase shifts.

You'll have to run that one by Cecil. He's said many times that
traveling waves bounce off each other when they meet.

That's just part of your Big Lie. Traveling waves
superpose. They do NOT "bounce off each other".
--
73, Cecil http://www.w5dxp.com